1. Unit 1 Research Methods (can be examined in Unit 1&2)
Correlations
Unit 1 Research Methods (can be examined in Unit 1&2)

4. There is a positive correlation between shoe size and reading age

6. Just because there’s a correlation, this does NOT mean that one variable CAUSED another
Explore the “Spurious Correlations” website

8. Even if there is a cause and effect relationship, have you got cause and effect the right way around?

9. What is a correlation?
Where two variables are plotted against each other to see if there may be a relationship
Pairs of data are plotted on a scattergraph
Predictions can be made based on the data you have

10. Types of correlation

11. Just because there’s a correlation, this does NOT mean that one variable CAUSED another
A cause and effect relationship cannot be established as the data was not collected in an experiment and extraneous variables have not been accounted for.
The relationship could:
a coincidence
have a 3rd related variable
be cause and effect

12. Extension
A statistical test, e.g. Spearman’s rank correlation test or Pearson’s test can be used to mathematically decide if there is a correlation.
These tests result in a number between 1 and -1 (1 = perfect +ve correlation, 0=no correlation, -1= perfect –ve correlation)
A ‘critical value’ (cut off point) can be looked up depending on sample size

13. Evaluating the use of correlations
Can be used to look for a relationship which a researcher can then do an experiment to try and establish causal relationship
Can be used when it would be unethical or impossible to carry out an experiment, e.g. with diseases
Cannot be used to determine cause and effect relationship
Needs a very large sample size

14. Text book pages 88-91